000 AXNT20 KNHC 262343 TWDAT TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 805 PM EDT MON SEP 26 2011 TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL ANALYSIS. BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 2300 UTC. ...SPECIAL FEATURES... TROPICAL STORM PHILIPPE IS CENTERED NEAR 15.4N 34.4W AT 26/2100 UTC OR ABOUT 600 NM W OF THE CAPE VERDE ISLANDS MOVING NW AT 7 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED WIND SPEED IS 50 KT WITH GUSTS TO 60 KT. NUMEROUS STRONG CONVECTION IS FROM 13N-16N BETWEEN 32W-35W...WITH MODERATE CONVECTION ELSEWHERE FROM 12N-17N BETWEEN 32W-35W. SEE LATEST NHC FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. A 1011 MB LOW...REMNANT LOW OF OPHELIA...IS CURRENTLY CENTERED NE OF THE NRN LEEWARD ISLANDS NEAR 19N60W. A SURFACE TROUGH EXTENDS THROUGH THE LOW CENTER ALONG 21N57W 17N60W TO 17N65W DEPICTING SOME OF THE LINES OF CONVERGENCE INTO THE LOW CENTER. CURRENTLY NUMEROUS STRONG CONVECTION IS SE OF THE CENTER FROM 17N-19N BETWEEN 57W-60W...WITH SCATTERED MODERATE CONVECTION ELSEWHERE FROM 15N-21N BETWEEN 56W-62W. THE LOW IS EXPECTED TO DRIFT W-NW OVER THE NEXT COUPLE OF DAYS AND HAS THE POTENTIAL FOR FURTHER DEVELOPMENT. EVEN THOUGH IT IS EXPECTED TO STAY N OF THE ISLANDS...CONVECTION ASSOCIATED WITH THE LOW COULD IMPACT THE LEEWARD ISLANDS. ...TROPICAL WAVES... TROPICAL WAVE IS ANALYZED FROM 17N47W TO 11N45W MOVING W AT 5-10 KT. THE WAVE REMAINS WEAK AND WITH LOW-AMPLITUDE...BUT IS STILL DISCERNIBLE IN SATELLITE IMAGERY AND SATELLITE WINDS. VERY DRY AIR IS ALOFT OVER THE WAVE WHICH IS INHIBITING DEEP CONVECTION. FORECAST GUIDANCE INDICATES THAT THE WAVE WILL CONTINUE TO MOVE W-NW OVER THE NEXT COUPLE OF DAYS BEFORE DISSIPATING LATER IN THE WEEK. ...ITCZ/MONSOON TROUGH... THE MONSOON TROUGH HAS BEGUN TO BUILD BACK IN BEHIND T.S. PHILIPPE AND CURRENTLY EXTENDS FROM THE AFRICAN COAST NEAR 13N17W TO 11N24W. A FEW WIDELY ISOLATED SHOWERS ARE FROM 2N-12N BETWEEN 19W-32W. ...DISCUSSION... GULF OF MEXICO... MAINLY WLY FLOW ALOFT DOMINATES THE GULF OF MEXICO THIS EVENING WITH AN UPPER LEVEL TROUGH TO THE N OVER THE ERN CONUS AND AN UPPER LEVEL RIDGE TO THE S CENTERED OVER SRN MEXICO. WATER VAPOR IMAGERY INDICATES MOSTLY DRY AIR ALOFT COVERS THE BASIN WHICH IS HELPING MAINTAIN MOSTLY FAIR CONDITIONS W OF 88W WITH WEAK ANTI-CYCLONIC SURFACE FLOW. HOWEVER...A SHORTWAVE UPPER TROUGH IS EXTENDING SWD FROM THE MAIN TROUGH WHICH HAS HELPED MAINTAIN A SURFACE TROUGH EXTENDING FROM NRN FLORIDA NEAR 31N83W ACROSS THE BIG BEND OF FLORIDA TO NEAR 25N84W. SCATTERED SHOWERS/THUNDERSTORMS...SOME HEAVY...ARE E OF THE TROUGH AXIS ACROSS THE ENTIRE FLORIDA PENINSULA AND STRAITS OF FLORIDA INTO CUBA. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE ALSO W OF THE TROUGH AXIS FROM 23N-26N BETWEEN 84W-88W. EXPECT MOIST CONDITIONS TO REMAIN ACROSS FLORIDA OVER THE NEXT 24 HOURS WITH WEAK SURFACE RIDGING BUILDING OVER THE REMAINDER OF THE GULF. CARIBBEAN SEA... UPPER LEVEL RIDGING EXTENDING FROM SRN MEXICO EXTENDS OVER THE NW CARIBBEAN WHERE MOSTLY FAIR WEATHER PREVAILS. A FEW SHOWERS/THUNDERSTORMS EXTEND S OF WRN CUBA DUE TO MOISTURE TO THE N OVER THE FAR ERN GULF AND FLORIDA. TO THE S...CONFLUENCE NEAR THE MONSOON TROUGH AXIS EXTENDING FROM COSTA RICA TO NRN COLOMBIA IS HELPING PRODUCE SCATTERED SHOWERS/THUNDERSTORMS S OF 16N BETWEEN 71W-81W...AND S OF 13N W OF 81W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE ALSO ACROSS COSTA RICA AND NICARAGUA. SOME OF THE ACTIVITY N OF THE MONSOON TROUGH IS BEING FURTHER ENHANCED BY DIFFLUENCE ALOFT AROUND THE BASE OF AN UPPER LEVEL TROUGH EXTENDING ACROSS ERN HISPANIOLA TO N OF THE COLOMBIA/VENEZUELA BORDER. THE FAR ERN CARIBBEAN IS UNDER CLEAR SKIES THIS EVENING WITH MODERATE DRY AIR ALOFT. THE REMNANT LOW OF OPHELIA IS CURRENTLY NE OF THE NRN LEEWARD ISLANDS WHICH MAY BRING SHOWERS/THUNDERSTORMS TO THE ISLANDS OVER THE NEXT DAY OR SO. SEE THE SPECIAL FEATURES SECTION FOR MORE DETAILS ON THE SYSTEM. ATLANTIC OCEAN... A NARROW UPPER LEVEL RIDGE EXTENDS FROM CENTRAL CUBA ACROSS THE NW BAHAMAS TO NEAR 32N76W. A SHORTWAVE UPPER TROUGH LIES TO THE W NEAR THE W COAST OF FLORIDA. THIS PATTERN IS PRODUCING DIFFLUENT FLOW ALOFT OVER THE FLORIDA PENINSULA AND THE COASTAL WATERS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE CURRENTLY W OF 30W AND ACROSS FLORIDA. ANOTHER UPPER LEVEL TROUGH IS TO THE E ALONG 71W. DIFFLUENT FLOW AROUND THE ERN SIDE OF THIS TROUGH IS ALSO HELPING SUPPORT ISOLATED SHOWERS/THUNDERSTORMS FROM 19N-25N BETWEEN 65W-70W. AT THE SURFACE...RIDGING DOMINATES AROUND A 1020 MB HIGH CENTERED NEAR 32N68W. NE OF THE LEEWARD ISLANDS A 1011 MB LOW...REMNANTS OF OPHELIA...IS CENTERED NEAR 19N60W. SEE SPECIAL FEATURES ABOVE FOR MORE DETAILS. FARTHER E...AN UPPER LEVEL RIDGE COVERS THE CENTRAL ATLC CENTERED NEAR 28N55W WITH ANOTHER UPPER LEVEL TROUGH ALONG 34W. THIS UPPER TROUGH IS SUPPORTING A SURFACE LOW N OF THE DISCUSSION AREA. A COLD FRONT ASSOCIATED WITH THE LOW EXTENDS ALONG 32N32W 27N36W 24N46W. ISOLATED SHOWERS ARE WITHIN 120 NM E OF THE FRONT. WEAK SURFACE RIDGING AROUND A 1022 MB HIGH N OF THE MADEIRA ISLANDS COVERS THE FAR ERN ATLC SUPPORTED BY AN UPPER LEVEL RIDGE ALONG 21W. FOR ADDITIONAL INFORMATION PLEASE VISIT HTTP://WWW.HURRICANES.GOV/MARINE $$ WALTON